The present invention concerns a method and arrangement to accomplish a self-acting, one-way flow in a conduit, with minimal flow resistance.
The existing self-acting check valves of the one-way type are dominated by tilting gates and check valves having a ball, a rubber diaphragm or a floating body. In common for all the above check valves is that they give rise to a flow resistance of large or small extent, in the conduit in which they are mounted. Furthermore, flow resistance, in large or small extent, gives rise to problems regarding clogging. Since reliability often is a quality sought after this leads to a demand for other solutions.
Especially check valves designed for mounting inside a conduit give rise to large flow restrictions. When applied for pressurised conduits the capacity of the pumps and sometimes the outer dimensions of the conduits must be amended to achieve a satisfying functionality. Due to the above this type of check valves are rarely used in practice, even tough they have considerable and sought after advantages. There are check valves having negligible flow resistance, however they have either a well or a chamber and are expensive both as such and to install in existing conduits.
Thus, one object of the present invention is to provide a simple and yet reliable method and means, by which a self-acting one-way flow may be established without giving rise to more than negligible flow resistance.
A further object of the invention is to make retrofit of such a one-way valve possible in an existing conduit without the need of any redesigns or changes of dimensions in connection to the assembly.
According to the invention a one-way valve, which in an unaffected condition closes off the conduit, is of a flexible, elastic material and is arranged with a tight fit to the inner surface of the conduit. It is partially fixed along the inner periphery of the conduit by means of one or more parts of its outer surface having a longitudinal/circumferential extension in the conduit, in such a way that in case of pressure from a medium in the conduit in a first direction a possible flow is blocked due to the pressure of the medium pressing the non fixed parts of the one-way valve against the inner surface of the conduit. Thus, a completely tight element is formed. Under influence of pressure of the medium in the opposite direction the non fixed parts of the one-way valve are brought to collapse/fold, whereby a flow, depending of the magnitude of the pressure is let through with negligible resistance.
According to a preferred embodiment of the invention the partial fixing of the one-way valve is done along half or less of the inner circumference of the conduit, whereby the one-way valve more or less will be in contact with the inner surface of the conduit when flow is allowed, depending on the pressure of the flow. By this feature, at maximum flow the one-way valve will be folded completely onto the inner surface of the conduit, whereby its radial extension in the conduit is almost negligible.
According to a further preferred embodiment of the invention the one-way valve is designed with an inherent elasticity returning it to its non deformed position, in which the one-way valve completely closes the conduit, when unaffected. This feature means that the material as such has an xe2x80x9cinherent return springxe2x80x9d, which closes the check valve in lack of flow and thus gives rise to no xe2x80x9cminor flowersxe2x80x9d in the blocked direction.
In a further embodiment the one-way valve in the partially fixed area or areas is fixed to the inside of the conduit along the entire length of the one-way valve. This gives the advantage that the one-way valve will adhere to a surface corresponding to almost the entire extent of the one-way valve in folded form, which in turn means that the strength of the bond between the one-way valve and the conduit is enhanced by the flow of the conduit.